One particular type of light fixture is known as a lay-in luminaire, or a troffer. A troffer is typically installed within a suspended ceiling grid system where one or more ceiling tiles are replaced with the troffer. Thus, the exterior dimensions of the troffer are typically sized to fit within the regular spacing of the ceiling tiles. In the United States, the spacing of the ceiling grid is often two feet by two feet and, therefore, troffers used in the United States typically have dimensions that are a multiple of two feet. For example, many troffers are two feet by two feet or two feet by four feet. Although one example of a typical ceiling grid spacing is provided, the spacing can be greater or less in other examples. The troffer typically houses one or more fluorescent tubes for providing illumination to a desired illuminated area.
Although, fluorescent tubes are more efficient than some types of lamps, such as incandescent light bulbs, they are still less efficient than solid state light emitters, such as LEDs. A significant percentage of electricity that is generated in the United States goes towards lighting applications. As the demand for and the cost of generating electricity has risen over the years, utility companies and other governmental agencies have begun promoting the use of more efficient ways to generate light. Thus, there has been a shift of consumers desiring to use light fixtures having solid state light emitters from light fixtures using other types of lamps, such as fluorescent tubes.
Conventional approaches to providing solid state light emitters in a suspended ceiling grid system include replacing fluorescent tubes found within typical troffers with an LED lamp shaped into the size of the fluorescent tube. Such an approach utilizes existing fluorescent troffer fixtures and replaces just the lamp. Another approach to providing solid state light emitters for a suspended ceiling grid system includes providing a solid state lighting luminaire that looks similar to a lensed troffer, where a lens sheet is provided between the solid state light sources and the desired illuminated area. The solid state light sources are oriented and pointed towards the desired illuminated area. In this approach, a heat sink is generally coupled to the troffer along its top side so that it lies above the ceiling plane and is not visible to an end-user standing within the desired illuminated area.
A challenge with solid state light emitters is that many solid state light emitters do not operate well in high temperatures. For example, many LED light sources have average operating lifetimes of decades, but some LEDs' lifetimes are significantly shortened if they are operated at elevated temperatures. Thus, efficient heat removal from the LEDs enable longer LED lifetimes. One issue arising in conventional approaches for providing solid state light emitters in a suspended ceiling grid system is that the heat is transferred from the LEDs to the heat sink located above the ceiling plane; thereby, causing the heat to be trapped within the ceiling area. Hence, the operating temperature of these LEDs soon increase, thereby shortening the life of these LEDs.
A further challenge with solid state light emitters arises from the relatively high light output from a relatively small area provided by solid state emitters. Such a concentration of light output presents challenges in providing solid state lighting systems for general illumination in that large changes in brightness in a small area is perceived as glare and distracting to occupants. It is a challenge to provide uniform lighting when using solid state light emitters within a ceiling grid system.